The present invention relates to a pressure sensor module.
A pressure sensor device that includes a semiconductor chip having a pressure sensor is described in International Published Patent Application No. WO 98/00692. The arrangement is intended for mounting on a p.c. board. The electric leads of the semiconductor chip are not hermetically injected in the plastic of the housing. In the presence of a partial vacuum in the area of the pressure sensor, air may be drawn along the leads into the gel, mechanically stressing the bonding wires, i.e., bonds. In addition, the separating membrane corrupts the pressure characteristic of the semiconductor chip, due to its rigidity. In situations that require stricter measuring accuracy, it may therefore be required to increase the membrane diameter and reduce the membrane thickness. This may have a negative effect on miniaturization.
A pressure sensor chip that is mounted and fastened as a single unit in a pressure sensor module housing is described from mstnews 2/99, pages 8 to 9. It may not be possible to calibrate the pressure sensor until after the pressure sensor chip has been mounted, since mounting the pressure sensor chip and passivating it with a covering arrangement may influences a calibration curve. Therefore, the entire module housing, including the attached pressure sensor, may need to be exposed to different temperatures and pressures to achieve calibration. The long waiting period for heating the large sensor housing and the low packing density for calibration may make this very expensive.
In the case of the conventional pressure sensor, the reject rate during calibration may also not be detected until after the sensor chip is mounted. When this happens, the expensive pressure sensor module housing may no longer be usable. This may increases costs due to rejection.
A pressure sensor module in which the pressure sensor is sealed pressure-tight by a cover is described in German Published Patent Application No. 197 314 20. This mounting method may be expensive, as may be the use of a ceramic substrate. In addition, the frame surrounding the gel may need to be separately attached to the ceramic substrate.
A pressure sensor module according to the present invention may provide a simple arrangement for mounting a pressure sensor in a module housing and producing a pressure sensor module.
A sensor housing may be made of plastic because the latter may be easy to produce.
Electric leads may be surrounded, at least in part, by the sensor housing, which holds them in place and enables the leads to pass through the sensor housing.
To protect a pressure sensor in its sensor housing against external ambient conditions and encapsulate it in a pressure-tight manner, the sensor housing may be surrounded by an encapsulating compound. In addition, the encapsulating compound may achieves a gas-tight passage for the leads.
The pressure sensor may have elements for improving electromagnetic compatibility.
As elements for improving electromagnetic compatibility, capacitors are advantageously connected electrically and mechanically to the electric leads by conductive adhesive, soldering or welding.
A media-resistant gel, such as fluorosilicone gel, may be used as the covering arrangement for the pressure sensor chip, so that other protection measures may be rendered unnecessary.